The relation between the stretching vibration frequency of X=O double bond of alkyl substituted compounds R'X=O and the Polarizability Effect Index (PEI) of alkyl group R can be expressed as ν=a+bPEI(R), where X represents C and N elements. The results showed that the Polarizability Effect Index (PEI) of alkyl group R decreases the stretching vibration frequency of X=O bond.

Key words: ALKYL, CHEMICAL BONDS, FREQUENCY OF VIBRATION, EXPONENT, POLARIZATION EFFECT